Method for the limited oxidation of saturated aliphatic hydrocarbons with formation of aldehydic compounds



Dec. 5, 1950 F. M. MCNALL 2,532,930

METHOD FOR THE LIMITED OXIDATION OF SATURATED ALIPHATIC HYDROCARBONS WITH FORMATION 0F ALDEHYDIC compounos Filed Aug. 9, 1944 2 Sheets-Sheet 1 INVENTOR. Ifiredkg fl MZ Dec. 5, 1950 MONALL 7 2,532,930

METHOD FOR THE LIMITED OXIDATION OF SATURATED ALIPHATIC HYDROCARBONS WITH FORMATION 0F ALDEHYDIC COMPOUNDS Filed Aug. 9, 1944 I 2 SheetsSheet 2 JJ 3f :E To

PRODUCT fa e 4f JIZ S 109% v Patented Dec. 5, 1950 METHOD FOR THE LIDIITED OXIDATION OF SATURATED ALIPHATIC HYDROCARBONS WITH FORMATION OF ALDEHYDIC COM- POUNDS Fredlee M. McNall, Olean, N. Y., assignor new Bros. 00., Inc., a corporation of New York Application August 9, 1944, Serial No. 548,694

1 25 Claims.

The present invention relates to improvements in the oxidation of hydrocarbon gases and more particularly of the saturated hydrocarbon gases, methane and ethane. It is particularly applicable to the oxidation of methane and methanecontaining gases, such as natural gas. It will be fully understood from the following description, and the accompanying drawings in which apparatus for carrying the invention into effect is diagrammatically illustrated.

This application is a continuation-in-part of my prior application Serial No. 463,276, filed ctober 24, 1942, now abandoned.

In processes for the oxidation of methane, particularly for the production of formaldehyde and other oxidized derivatives thereof, as hitherto conducted, the oxidation has been effected by bringing the hydrocarbon together with oxygen or oxygen-containing gases, such as oxides of nitrogen, in contact with a catalyst. In some cases sulfuric acid has been uses as the catalyst, but in all cases, the oxygen or oxygen-containing 1 acid may be employed. Effective results can be gas supplied in admixture with the hydrocarbon sulfuric acid did not function as the oxidizing.

agent.

I have now discovered that a limited oxidation of methane, ethane and like saturated hydrocarbon gases may be effected directly by meansof sulfuric acid and of sulfur trioxide under suitable temperature conditions, without the use of additional oxygen or oxygen-bearing materials to supply the oxygen for oxidation. In carrying out the operation in accordance withthe present invention, the sulfuric acid or sulfur trioxide itself constitutes the oxidizing agent and appreciable proportions of other oxygen-bearing or supplying material, including oxygen, are not present; and in addition to the oxidation products derived from the hydrocarbons, of which formaldehyde predominates if methane is the principal constituent of the hydrocarbon gas, sulfur dioxide is formed by the reduction of the sulfuric acid. The sulfur dioxide may, of course, be separated from the products of oxidation, and, if desired, converted into sulfuric acid and reused in the process.

In carrying out the present invention I preferably use concentrated sulfuric acid (93% to 98% although varying concentrations of the I and acetaldehyde.

secured by using concentrations of and higher. Concentrations of sulfuric acid above 98%, fuming sulfuric acid and sulfur trioxide may also be used. The lower concentrations are somewhat less effective.

The limited oxidation process of the invention may be effected at temperatures as low as 200 0., but I prefer to use temperatures ranging from 240 C. to the boiling point of the sulfuric acid in liquid phase operation. Higher temperatures, say to 500 to 600 C. may be used in the presence of sulfuric acid vapors or sulfur trioxide. In general it is found unnecessary to employ temperatures in excess of 320 to 340 C., and at excessively high temperatures the formation of undesirable by-products and carbonaceous materials may take place.

The pure hydrocarbon gases may, of course, be employed. However, I have found that natural gas may be satisfactorily used, for example, in the 1 production of forrnaldehyde from its methane content. Theethane present also appears to be oxidized with some formation of formaldehyde The higher hydrocarbons produce minor proportions of formaldehyde and varying proportions of other oxidation products.

Methyl alcohol is likewise produced from the oxidation of the methane, the proportions of methanol thus produced being greater at the lower temperatures at which the yields of formaldehyde are lower and vice versa. At temperatures at which high yields of formaldehyde are secured, from 260 C. upwardly, the methanol formation is practically negligible.

The process may be carried out in any suitable apparatus, closed to the air, in which the hydrocarbon gases may be contacted with sulfuric acid; for example, by merely bubbling the gases through a vessel, closed to the air, containing sulfuric acid heated to the desired reaction temperature. More effective contact may be secured by using vigorous agitation of the acid while contacting the hydrocarbon gases therewith; by

using diffusers to reduce the bubble size of the gases introduced; -or by suitable packings, such as glass beads or rings, carbon rings or the like, which give greater contact surface and aid in effective distribution of the gas. The process may also be carried out by effecting direct contact ,with S0: or with sulfuric acid vapors at high temperatures.

In the accompanying drawings,

Fig. 1 illustrates diagrammatically apparatus suitable for carrying out the invention continuously, and

' Fig. 2 illustrates diagrammatically a modified form of apparatus for carrying out the invention.

In Fig. 1 of the drawings, the numeral I indircates an insulated reaction tower, and is shown partly in elevation and partly in section. The remainder of the equipment is shown in diagrammatic form.

The hydrocarbon gas, such as natural gas, enters the tower I through the line 2. The tower I is provided with an insulating jacket 3 and may be heatedby any suitable means, for example, the electrical resistance elements 4 embedded within the insulating jacket. Other means of heating may be employed, for example, a heated liquid such as diphenyl or diphenyl oxide may be circulated through a jacket surrounding the tower. The line entering the tower I passes through an opening in a sealed closure 5 at the base of the tower. A short distance above this closure is provided a perforated supporting plate 5. upon which rests the packing, which may suitably be beads or rings of glass, carbon or other inert material. Before beginning the operation. sulfuric acid is ,supplied to the tower, sui ablv t rough line I.

The sulfuric acid in the tower is heated to and maintained at the desired reacting temperature and the hydrocarbon gas is passed through the tower to contact with the heated sulfuric acid at a rate which will secure effective oxidation. The treated gas, which contains any unreacted hydrocarbons as well as the oxidation products, then passes out of the tower through the line 8 and through a cooler and condenser 9, in which the out oing products are cooled and some higher boiling contituents may be condensed. The cooled products from the cooler and condenser pass through line 10 into a container II, in which they are discharged below the level of a body of water or other stripping fluid. The liquid in container H, in which the major proportion or all of the aldehyde products are absorbed, may be discharged through valved outlet pipe l2 to a suitable still (not shown) for rectification of the product. Gas and uncondensed vapors pass from vessel I l through line 22 into a second vessel l3, in which a body of water is maintained. The gases enter the vessel l3 below the surface of the body of water to remove any remaining soluble oxidation products from the gases. The liquid may be discharged to the product still or to container II for further use. Some sulfur dioxide is also removed fromthe gases in vessels l I and I3 and may be recovered from the product still.

The remaininggases then pass out of the vessel l3 through the line ll into the vessel in which they may be washed, for example, with an alkaline liquid such as a solution of sodium hydroxide. Here any remaining sulfur dioxide is removed. If desired, the gases may at this point be passed through concentrated sulfuric acid or other suitable drying medium to remove water vapor. The remaining gases, which consist almost entirely of unreacted hydrocarbons, pass out of the vessel l5 through the line l6 and are returned by it to the line I1 leading to the suetion side of a pump It! by which the gases are returned to the line 2 enterin the tower 'i. The hydrocarbon gases used for initially starting the operation and those supplied as make-up during the operation are supplied from the main gas line is which may suitably be provided with a meter 20. Sulfuric acid may be supplied through the line I at intervals or continuously during the operation, in which case a corresponding withdrawal of acid takesplace through line 2|. This withdrawn acid may be recirculated to line 1 until spent, or a portion may be continuously eliminated, corresponding make-up quantities of fresh acid being supplied. Sumcient make-up gas is supplied during the operation to maintain a substantially constant supply of gas to the tower. It will be understood, of course, that suitable meters and pressure gauges may be provided in the gas lines, as well as temperature indicating means, for the control of the operation.

It has been found advantageous to maintain .the acid level in the tower l at some intermediate point and to introduce the acid supplied during the run at a'point below the top, at or slightly above the acid level, as through line 1". The upper portion of the tower, which may be packed with suitable acid-resistant material or not, as desired, then serves to remove entrained acid from the outgoing vapors. It may be heated v to substantially the same temperature as that the trapped line 30.

designates a jacketed tower or receptacle into which the sulfuric acid used for theoxidation reaction is charged, for example, through the line 26. Vessel 25 may be heated in any desired manner, for example, by circulating through the jacket a heated fluid, such as diphenyl or diphenyl oxide. The hydrocarbon-containing gas is charged into the container 25 through the line 21 and passes through the body of sulfuric acid in the container. The gas may be discharged into the container through any suitable distributing device or diffuser (not shown), made of suitable acid resistant material and of a character to give a small bubble size, or the acid may be vigorously agitated by any suitable device.

The gases and vapors containing the formaldehyde and other products of the oxidation reaction pass out of the container 25 through the line 28 to a suitable elevated chamber 29, which may be insulated to maintain its temperature or which may be slightlycooled to aid-in the removal of entrained acid. .Any entrainment together with any condensate collected in the chamber 29 is returned to the tower or-oontainer 25 through The gases and vapors containing the aldehyde and other oxidation products pass out of the chamber 29 through the line 3| to a scrubbing tower 32, which may be of any suitable form; for example, a packed tower or a bubble plate tower. The gases and vapors pass upwardly through the scrubbing tower 32, in which they are scrubbed by a. suitable liquid, preferably water, which enters the tower through the line 33. The formaldehyde and other oxidation products are thereby removed from the gases in the form of an aqueous solution, which is discharged through the valved line 34 to a suitable product still (not shown), in which the formaldehyde may be concentrated to any desired degree. Sulfur dioxide will also be removed iron: the gases and vapors in the scrubbing tower 32, and the sulfur dioxide may be recovered in the operation of the product still and may be converted to sulfur trioxlde and sulfuric acid for reuse in the system.

The remaining gases, composed principally of unreacted hydrocarbon material, and which may carry with them some sulfur dioxide as well as water vapor, are passed from tower 32 through line 35 into the scrubber 36, in which they may be scrubbed with water or preferably with concentrated sulfuric acid to remove moisture before the gases are recirculated. The scrubbed gases pass out of the scrubber 36 through line 31 to a suitable blower or pump 38 by which they are forced through line 39 into the line 21 entering the base of the sulfuric acid tower 25. Additional or make-up gas is supplied continuously through the line 40, and mixes with the recirculated gas entering the line '21 from the line 39.

Gas may be vented from the system, as through the line 4], if desired.

Substantial oxidation of the saturated paraffinic hydrocarbon gases, particularly methane, is effected by sulfuric acid alone, with formation'of aldehydes, in the temperature range above indicated. I have also found that the formation of aldehydes and particularly of formaldehyde is improved by certain metallic compounds which apparently act by retarding excessive oxidation and formation of the oxides of carbon from the hydrocarbons. Such metallic compounds are designated herein as catalysts.

Catalysts which I have found effective are compounds of the metals having atomic weights above and particularly metals of the first and eighth periodic groups, cerium and lead. Those which I have found most effective are iron, cobalt, nickel, platinum, copper, silver, rubidium, and cerium. Palladium, lead and other metals of the groups above designated also have some effectiveness. These metals may be supplied to the acid as the metals themselves, preferably in finely divided form, or as salts or other suitable compounds, such as the sulfates, nitrates or the like, since the catalysts disperse themselves in the sulfuric acid or dissolve, probably as the sulfates. The proportion of these metallic catalysts employed may be very small, ranging from 0.001% upwardly, based on weight of sulfuric acid, and may range to as high as the solubility limit of the catalyst in the sulfuric acid. In the case of lead some suspended lead sulfate may be present. These metallic compounds, used singly, may greatly increase the yield of formaldehyde above that secured from sulfuric acid alone. However, I have found that by using the metals in admixture and particularly by using mixtures of the cobalt, nickel or iron compounds with silver compounds, or with silver and cerium compounds, the most efficient results are secured. When iron or iron compounds are used,-care must be taken to avoid accumulation of iron sulfate in the lines leading from the reaction tower. I find it convenient to use the sulfates, nitrates or chlorides of the metals, as well as the metals themselves, as apparently the compounds resulting from the action of the sulfuric acid are all effective. Thus I may use cobalt, nickel or iron sulfates or chlorides, silver nitrate, cerium sulfate, or the like. When mixtures of the metallic compounds are employed, I prefer to use a major proportion of tne cobalt, iron or nickel compound and a minor proportion of the silver, cerium or copper compound, although equal or greater proportions of the latter group may be used. Thus in general, in such mixtures, I prefer to employ one-tenth to one-fourth of the mixture as the copper or silver compound, or somewhat larger proportions of cerium compounds.

Using concentrated sulfuric acid alone, at temperatures of from 275 to 325 C., and with rates of flow of gas giving space velocities ranging from about 0.5 to about 8 per minute of gas to sulfric acid, effective conversions of methane into formaldehyde were secured. By space velocity, as used herein, is meant the volume of gas (V) passing in the stated unit of time through the volume of acid or acid plus catalyst (Va) presout, or V/Va. Appreciable conversion is secured at lower temperatures, down to 200 C. With the metal catalysts above referred to dissolved or suspended in the sulfuric acid, under similar rates of flow the proportions of the gas converted into formaldehyde were very substantially increased and the best results were secured by mixtures of the catalysts as above described. With the catalysts, as with the acid alone, varying rates of flow may be used and unreacted gas may be recycled, to secure higher yields from a given equipment.

In general, it is foundpreferable to operate with a low or moderate yield of formaldehyde per pass and with a high recycle rate, and with short periods of contact of the gas and acid or catalyst containing acid; i. e., with the higher space velocities. Thus, cycle rates giving a space velocity.

of 4 to 6.5 per minute have been found most effective, although space velocities of from 0.5 to 8 per minute have been effectively employed in equipment of the type illustrated in Fig. 2.

When the gas employed contains non-reactive diluents, these tend to build up in the system in recycling operations and occasional venting is required, as through line 4| in Fig. 2, to effect their removal. One indication of such a condition is an increase in the production of $02 in relation to formaldehyde produced. Any accumulation of oxides of carbon may be similarly removed. Raw gas is supplied to replace the gasso removed as well as that consumed in the reaction.

The catalysts used do not need to be of high purity, and the metals or their compounds may be used in their ordinar commercial grades.

Thus for example, using acid containing 0.1% of cobalt sulfate and 0.0005 to 0.001% silver nitrate, and with the acid maintained at 313 C., the yield of formaldehyde secured was 37.3% of the theoretical yield based on the methane content of the gas consumed in an operation in which the unreacted gas passing out of the treating tower was recycled, as in the apparatus illustrated in the drawing. At 300 C., with a substantially similar catalyst mixture, the yield of formaldehyde was 75.2% of the theoretical. At 275 C., with a similar catalyst mixture, the yield was 60.5%. No appreciable quantities of methanol were produced underthese conditions. As is apparent, the yield of formaldehyde increases with increase in temperature, and I prefer to operate above 240 C. and most suitably in the range of from 260 to 325 C.

In a series of runs employing concentrated sulfuric acid and with cycle rates giving a space velocity of 6.17 to 6.35 per minute and with the reaction zone maintained at about 295 C. (range 292 to 296 C.), using a commercial gas containing 75% methane, with some coke oven gas constituents, in equipment of the type illustrated in Fig. 2, and supplying make-up gas to replace methane as consumed, the following results were secured.

a. With sulfuric acid alone, formaldehyde yield 60% of theoretical (average of two runs).

b. With sulfuric acid containing 0.1% platinum choride, formaldehyde yield 89% of theoretical,

0. With sulfuric acid containing 0.1% rubidium chloride, formaldehyde yield 94% of theoretical.

With cerium salts, optimum temperatures of operation are somewhat lower. Thus in similar operations, with 0.1% ceric sulfate in the acid, at 265 to 270 C., the formaldehyde yield was in excess of 95% of theoretical. It will be understood that the assumed theoretical yield of formaldehyde is 1.875 parts by weight per part by weight of methane.

The series of runs above set forth are for purposes of illustration and have been selected to show variations in effective yields without and with various promoters while maintaining other conditions approximately the same, except where otherwise indicated.

Compounds of the metals hereinbefore referred to; i. e., of metals having atomic weight over 50, of the class comprising the first and eighth periodic groups cerium and lead, and particularly iron, cobalt, nickel, copper, silver, rubidium, palladium and cerium have been found effective when used individually and in admixture. In some cases the eifectiveness is shown by decrease in formation of carbon oxides or of degradation products of the sulfuric acid, such as sulfur and hydrogen sulfide.

The proportions of catalysts used may be varied, as indicated above. In general the proportions preferred are from 0.1 to 1.5 on the weight of the sulfuric acid. Thus the following mixed catalysts are illustrative of those which have been effectively employed (percentages are on the basis of the weight of sulfuric acid).

a. 0.1% CoSO4.7H2O and 0.0023% AgNOs b. 1% COSO4.7H2O and 0.02% AgNO:

0. 0.24% COSO4.'7H2O, 0.0023% AgNO3 and 0.1%

Ce (SO02 The same wide variations in proportions of the other individual catalysts have also been effec tively employed.

The use of purer methane gives somewhat better results and is preferred if the pure methane is readily available. The higher hydrocarbons, such as ethane, propane and butane, oxidize under similar conditions, but with smaller yields of formaldehyde. Thus, treatment of ethane under recycling conditions as described above, using a recycling rate giving a space velocity of 5.6 to 5.85 per minute, at about 320, gave a formaldehyde yield of 22% of theoretical (assuming formation of 2 mols of formaldehyde from each mol of ethane as theoretical). The catalyst used was 1.0 to CoS04.7HzO with 0.012 AgNO3 (basis sulfuric acid). In a similar run, using a catalyst mixture of 0.5% COSO47H2O, .0112% AgNO: and 01% Ce(SO4)-2, at about 325 0., a formaldehyde yield of 47% of theoretical was obtained. The conversion of ethane, propane and higher gaseous parafiin hydrocarbons may be similarly effected with the various catalysts and with the acid alone, as in the case of methane, but generally with somewhat lower yields, based on theoretical and with greater S02 production, and optimum temperature are somewhat lower. As is apparent, natural gas may be employed with fairl effective utilization of the higher hydrocarbons as well as of the methane.

The operation may also be conducted in vapor phase, as hereinbefore stated. Thus, passing a methane-containing gas (75% methane) through boiling sulfuric acid and then passing the resulting mixture of vapors (including sulfuric acid and sulfur trioxide) through a zone heated to 500 C., in a recycling operation, yields of formaldehyde of 60-62% of theoretical were obtained.

In using the catalysts, as above set forth, I add them in the desired proportions in the acid charged into the reaction tower or vessel, and also in any make-up acid which may be supplied in the continuous operation of the process, as hereinbefore described.

The course of the reaction is not appreciably affected by the presence of gaseous impurities such as are found in pipe line gases or by the admixture with the gases treated of carbon monoxide, hydrogen or aromatics derived from coke oven gas. Thus, using pipe line gases which have been admixed with 10 to 20% of coke oven and producer gas, the methane and other aliphatic constituents react in the same way as do the pure hydrocarbons and natural gas.

In the accompanying claims, where a metalcontaining catalyst is referred to, it is to be understood that the compound actually present is that resulting from the introduction of the metal or its compound into the sulfuric acid. In the term methane-containing gas I include methane as well as gases containing methane.

Iclaim:

1. The method of producing oxygenated derivatives of aliphatic hydrocarbons in which the oxygen is bonded to a carbon atom of the hydrocarbon by effecting a limited oxidation of such saturated aliphatic hydrocarbon gases in which such gases are directly contacted with an oxygenated sulfur acid of the class consisting of sulfuric acid and sulfur trioxide as the oxygen supplying agent at a temperature in excess of 200 C. and not over 600 C. in the absence of other oxygen bearing materials in substantial quantities.

2. The method of oxidizing methane in which methane-containing gas is directly contacted with sulfuric acid as the oxygen supplying agent at a temperature of not less than 24 C. and notover 600 C., with formation of formaldehyde, in the'absence of other oxygen bearing materials in substantial quantities.

3. The method of producing formaldehyde by direct oxidation of gaseous saturated paraflin hydrocarbons which comprises contacting methanecontaining gas with sulfuric acid as the oxygen supplying agent containing as a catalyst a metal compound of a metal of the class consisting of the metals of the 1st and 8th periodic groups and cerium, having an atomic weight over 50, at a temperature of at least 240 C. in the absence of other oxygen bearing materials in substantial quantities.

4. The method of producing formaldehyde by direct oxidation of methane which comprises contacting methane-containing gas with sulfuric acid as the oxygen supplying agent containing as a catalyst a cobalt compound, at a temperature of at least 240 C. in the absence of other titles.

5. The method of producing formaldehyde by direct oxidation of methane which comprises contacting methane-containing gas with sulfuric acid as the oxygen supplying agent containing as a catalyst a nickel compound, at a temperature of at least 240 C. in the absence of other oxygen bearing materials in substantial quantities.

6. The method of producing formaldehyde by direct oxidation of methane which comprises contacting methane-containing gas with sulfuric acid as the oxygen supplying agent containing as a catalyst an iron compound, at a temperature of at least 240 C. in the absence of other oxygen bearing materials in substantial quantities.

7. The method of producing formaldehyde by direct oxidation of methane which comprises contacting methane-containing gas with sulfuric acid as the oxygen supplying agent containing as a catalyst a silver compound, at a temperature of at least 240 C. in the absence of other oxygen bearing materials in substantial quantities.

8. The method of producing formaldehyde by direct oxidation of methane which comprises contacting methane-containing gas with sulfuric acid as the oxygen supplying agent containing as a catalyst a copper compound, at a temperature of at least 240 C. in the absence of other oxygen bearing materials in substantial quantities.

9. The method of producing formaldehyde by direct oxidation of methane which comprises contacting methane-containing gas with sulfuric acid as the oxygen supplying agent, containing as a catalyst a cerium compound, at a temperature of at least 240 C. in the absence of other oxygen bearing materials in substantial quantities.

10. The method of producing formaldehyde by direct oxidation of methane which comprises contacting methane-containing gas with sulfuric acid as the oxygen supplying agent, containing as a catalyst a rubidium compound, at a temperature of at least 240 C. in the absence of other oxygen bearing materials in substantial quantities.

11. The method of producing formaldehyde by direct oxidation of methane which comprises contacting methane-containing gas with sulfuric acid as the oxygen supplying agent, containing as a catalyst a platinum compound, at a temperature of at least 240 C. in the absence of other oxygen bearing materials in substantial quantities.

12. The method of producing formaldehyde by direct oxidation of methane which comprises contacting methane-containing gas with sulfuric acid as the oxygen supplying agent containing as a catalyst cobalt and silver compounds, at a temperature of at least 240 C. in the absence of other oxygen bearing materials in substantial quantities.

13. The method of producing formaldehyde by direct oxidation of methane which comprises contacting methane-containing gas with sulfuric acid as the oxygen supplying agent containing as a catalyst nickel and silver compounds, at a temperature of at least 240 C. in the absence of other oxygen bearing materials in substantial quantities.

14. The method of producing formadehyde which comprises contacting methane-containing gas in a closed system with concentrated sulfuric acid as the oxygen supplying agent at a temperature in excess of 240 C. and not over 340 0., in the absence of other oxygen bearing materials in substantial quantities, removing unreacted gas and vaporized products of reaction, separating formaldehyde therefrom, subsequently separating unreacted gases from other reaction products and recycling the unreacted gases for retreatment with the sulfuric acid.

15. The method of producing formaldehyde which comprises contacting methane-containing gas in a closed system with concentrated sulfuric acid as the oxidizing agent at a temperature of 260 to 340 C. at space velocities of 0.5 to 8 per minute in the absence of other oxygen-bearing materials in substantial quantities, removing unreacted gas and vaporized products of reaction, separating formaldehyde therefrom, and recycling the unreacted gases for retreatment with the sulfuric acid.

16. The method of producing formaldehyde which comprises contacting methane-containing gas in a closed system with concentrated sulfuric acid as the oxidizing agent at a temperature of 260 to 325 C. at space velocitiesof 4 to 6.5 per minute in the presence of a metallic catalyst, the metal thereof being selected from the group consisting of the metals of the first and eighth periodic groups having an atomic weight over 50, and cerium, and in the absence of other oxidizing agents in appreciable quantities, removing unreacted gas and vaporized products of reaction, separating formaldehyde therefrom, and recycling the unreacted gases for retreatment with the sulfuric acid.

17. The method of producing formaldehyde which comprises contacting methane-containing gas with concentrated sulfuric acid containing as a catalyst a metal selected from the group consisting of the metals of the 1st and 8th periodic groups having an atomic weight over 50, and cerium, at a temperature of 260 to 325 C.

18. The method of oxidizing saturated aliphatic hydrocarbon gases to form aldehydic products which comprises subjectingsuch gas to direct contact with an oxygenated sulfur acid of the class consisting of sulfuric acid and sulfur trioxide as the oxygen-supplying agent, in the presence of cobalt and silver compounds as catalysts, at a temperature in excess of 200 C., in the absence of other oxygen bearing materials in substantial quantities.

19. The method of oxidizing methane to produce formaldehyde which comprises contacting a methane-containing gas with sulfuric acid as the oxygen supplying agent and containing as a catalyst cobalt and silver compounds, at a temperature of at least 200 C., in the absence of other oxygen bearing materials in substantial quantities.

20. The method of oxidizing methane to produce formaldehyde which comprises contacting a methane-containing gas with sulfuric acid as the oxygen supplying agent and containing as a catalyst a cobalt compound, at a temperature of at least 200 C., in the absence of other oxygen bearing materials in substantial quantities.

21. The method of oxidizing methane to produce formaldehyde which comprises contacting a methane-containing gas with sulfuric acid as the oxygen supplying agent and containing as a catalyst a silver compound, at a temperature of at least 200 C., in the absence of other oxygen bearing materials in substantial quantities.

22. The method of oxidizing methane to produce formaldehyde which comprises contacting a methane-containing gas with sulfuric acid as the 11 oxygen supplying agent and containing as a catalyst .a metal of the 8th periodic group having an atomic number below 30. at a temperature of at least 200 C., in the absence of other oxygen bearing material in substantial quantities.

23. The method of oxidizing methane to produce formaldehyde which comprises contacting a methane containing gas with sulfuric acid as the oxygen supplying agent and containing as a catalyst a metal of the 8th periodic group having an atomic number below 30 and silver, at a temperature of at least 200 C., in the absenceofother oxygen bearing materials in substantial quantities.

24. The method of producing oxygenated derivatives of aliphatic hydrocarbons in which the oxygen is bonded to a carbon atom of the hydrocarbons by efiecting a limited oxidation of satrated aliphatic hydrocarbon gases in which such gases are directly contacted with an oxygenated sulfur acid of the class consisting of sulfuric acid and sulfur trioxide as the oxygen supplying agent at a temperature in excess of 200 C. and at space .velocities of 0.5 to 8 per minute in the absence of other oxygenated bearing materials in substantial quantities.

25. The method of oxidizing methane in which methane-containing gas is directly contacted with sulfuric acid as the oxygen supplying agent .at a temperature of not less than 240 C. at space velocities of 0.5 to 8 per minute in the arisen!" Certificate of Correction Patent No. 2,532,930

. 4 12 01' other oxygen bearing materials in substantial quantities.

. FREDLEE M. McNALL.

REFERENCES CITED The following references are of record in the file of this. patent: V

STATES PATENTS Number, Name Date 1,324,715 Andrews Dec. 9,1919 2,270,705 Herstein Jan. 20, 1942 FQREllGN PATENTS Number Country Date 19,178 Great'Britain of 1902 297,442 Germany Feb. 22, 1913 OTHER REFERENCES December 5; 1950 i FREDLEE MC ALL It is hereby certified that error appears inthe printed-"specification of the above numbered patent requiring co'rreot1on as follows:

Column 1,

read constituents; column 8, line 53, for 24 C. read 240 0' line 21 for uses read used; column 3, line 39, for contituents and that the said Letters Patent should be read as corrected above, so that the same may conform to the recordof the case in the Patent Oifice.

Signed and'sealed this 23rd day of January, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

1. THE METHOD OF PRODUCING OXYGENATED DERIVATIVES OF ALIPHATIC HYDROCARBONS IN WHICH THE OXYGEN IS BONDED TO A CARON ATOM OF THE HYDROCARBON BY EFFECTING A LIMITED OXIDATION OF SUCH SATURATED ALIPHATIC HYDROCARBON GASES IN WHICH SUCH GASES ARE DIRECTLY CONTACTED WITH AN OXYGENATED SULFUR ACID OF THE CLASS CONSISTING OF SULFURIC ACID AND SULFUR TRIOXIDE AS THE OXYGEN SUPPLYING AGENT AT A TEMPERATURE IN EXCESS OF 200*C. AND NOT OVER 600*C. IN THE ABSENCE OF OTHER OXYGEN BEARING MATERIALS IN SUBSTANTIAL QUANTITIES. 